1. Field of the Invention
This invention relates to centrifuge bowl end closure attachment flanges, particularly such flanges located at the solids discharge end of the bowl of a solids-liquid separating centrifuge of the continuous solids discharging type.
2. Description of the Prior Art
Centrifuges of the type concerned commonly have a generally cylindrical bowl rotated at high speed about its axis to separate the solids toward the bowl by centrifugal force of a solids-liquid slurry continuously fed thereto; a conveyor helix rotated in the same direction at a slightly different speed to move the solids continuously to and out a frusto-conical end outlet from the bowl; and ports in the opposite bowl end, or internal scoops within the bowl for continuously discharging the separated liquid fraction. The bowl is provided with end members or "heads" which are usually provided with an annular radial flange bolted to a similar flange on the bowl to join the parts together. A stationary casing enclosure for the centrifuge has an annular baffle closely surrounding at least one of the joined flanges at the solids discharge end of the centrifuge to form an end compartment in the casing for receiving the discharged solids.
Such centrifuges are commonly applied to the treatment of slurries containing highly abrasive solids, as when used for dewatering coal. Despite the use of rotary plows in the solids receiving compartment of the centrifuge, these abrasive solids tend to accumulate at the compartment side of the casing baffle and between the baffle and the joined bowl flanges. Even though the flanges, like the bowl, are formed of metal (e.g., stainless steel) that is long wearing under normal circumstances, the so accumulated hard abrasive particles, pressing on the flanges rotating at high speed, wear awaythe flanges so rapidly that frequent repair or replacement is necessary. The cost of such frequent repair or replacement, added to the cost of centrifuge downtime necessary to accomplish it, in many cases is a major item of the expense of the centrifuge operation of the plant.
Known prior art efforts to solve the problem have not had satisfactory results. Generally these have involved welding hard wear-resistant material to the outer end surface of the flange, generally in the form of ribs of height just clearing the casing baffle. In one such arrangement, the ribs were located at frequent intervals transversely across the flange end and were angled to act as an air pump. However, it has been generally found that welded-on wear-resistant materials do not add greatly to wear life, having inherent susceptibility to fracture under load and insufficient resistance to the concentrated wear forces involved.